Process and tubular reactor for recovery of chlorine from iron chlorides

ABSTRACT

The present invention relates to a process for recovering chlorine from a feed stream containing metal chlorides using a tubular reactor wherein a hot oxygen containing gas has an initial velocity such that the resulting velocity of the bulk gas formed from mixing the oxygen containing gas with the metal chloride feed stream and a scrubs feed stream is sufficient to remove wall deposits as fast as such deposits are formed.

BACKGROUND OF THE INVENTION

This invention relates to a process for the recovery of chlorine frommetal chlorides and the conversion of the metal chlorides to metaloxides using a high-velocity tubular reactor.

BACKGROUND OF THE INVENTION

Many industrial processes designed to convert mineral ores to productsof greater purity and value involves an initial step wherein metals inthe ore are converted to metal chlorides. The processes for theproduction of titanium dioxide pigment and for the production oftitanium or zirconium metal are examples of such conversion processeswhere metal values are first converted to metal chlorides.

The conversion of ore metal values to metal chlorides also provides ameans to separate iron and other metal chlorides from those of thehigher valued chlorides of metals such as titanium, and zirconium. But,there has continued to be the need for a process by which the chloridevalues from the iron and other metal chlorides considered to be of lowvalue could be recovered. One potential process would use oxygen oroxygen-containing gas at elevated temperature to convert the metalchlorides to metal oxides and chlorine. But, past attempts to developsuch a process have been plagued by adhesion of the product metal oxideto the reactor walls which severely limits the reactor utility. Thisinvention uses a tubular reactor where accumulation of adhesive productis prevented through use of high bulk gas velocity and addition ofscrubbing media. The scrubbing media is non-reactive solids present inthe metal chloride feed and/or non-reactive solids added to the reactor.

Iron chlorides and other metal chlorides are generated as byproductsfrom industrial processes involving chlorination, for example, in themanufacture of titanium dioxide pigment by the chloride process. Thesemetal chlorides have economic value due to their chlorine content and aneconomic loss may be incurred by their disposal. Recovery of recyclableelemental chlorine from the metal chlorides has long been sought becauseof potential economic and environmental benefits. However, economicaland practical ways of recovering chlorine from metal chlorides have notbeen provided by methods known in the art.

For a detailed discussion of the prior art and problems associated withoxidation of FeCl₃ and/or FeCl₂ to iron oxides and chlorine, see Bonsackand Fridman, U.S. Pat. No. 4,540,551, and Becker, et al., U.S. Pat. No.6,277,354.

Methods for oxidation of iron chloride to chlorine and ferric oxide in areactor, based on a feed stream comprising ferric chloride vapor, arewell known. In practice, however, such methods suffer from thedifficulty that in generating solid iron oxide product from the gaseousreactants there is a strong tendency for oxide scale to build up on thereactor walls and on associated equipment. These methods also sufferfrom the difficulty of requiring that the metal chlorides enter thereactor in the vapor phase, when typical byproduct metal chloridestreams contain components that are non-volatile or have high boilingpoints.

Herriman and Lawrence, U.S. Pat. No. 3,464,792, disclose a process forvapor phase oxidation of a metal halide. The process involves preheatinga first gas, that is, an oxidizing gas, the metal halide or an inertgas, using an electric arc device, e.g., gas plasma, to a temperature ofat least 2000° C. and then introducing the heated first gas into areaction zone. A second gas (oxidizing gas, metal halide or inert gas)is introduced to the reaction zone by means of an injection devicehaving a plurality of orifices. The injection device is positionedadjacent to the inlet of the first gas such that the second gas coolsmaterial forming on the walls of the injection device and is therebyheated before passing into the reaction zone.

Oxidation of iron chlorides to chlorine and ferric oxide based on a feedcomprising solid ferrous chloride is also known. Hsu, in U.S. Pat. No.4,994,255 discloses a process for oxidizing ferrous chloride to chlorineand ferric oxide, wherein solid ferrous chloride is introduced into afluidized bed reactor comprised of inert particulate material.

While various processes for recovering chlorine from metal chlorides aregenerally known, it is still desirable to improve upon these processesto make them more attractive economically as a means to recover andrecycle chlorine. Particularly, it would be desirable to have a processfor treating metal chlorides to generate chlorine with improvements inreduction of wall scale and pluggage problems, high conversion of themetal chlorides, generation of recyclable chlorine, and ability torecycle unreacted oxygen in a simple reaction system. The presentinvention provides such a process.

BRIEF SUMMARY OF THE INVENTION

The present invention is a process for recovering chlorine by oxidizinga stream comprising metal chlorides, comprising the steps of:

(a) feeding a pre-heated oxygen containing gas into one end of a tubularreactor;

(b) contacting the pre-heated oxygen containing gas at temperatureT_(Ox) and velocity v_(Ox) and a stream comprising metal chlorides attemperature T_(mx) and velocity V_(mx) wherein the metal chlorides areselected from the group consisting of iron chlorides and mixtures oftransition, alkali and alkaline-earth metal chlorides existing in theform of entrained solids, entrained liquids, vapors and mixturesthereof;

(c) introducing non-reactive scrubbing media at temperature T_(s) andvelocity v_(s) into the reactor; and

(d) at least partially reacting the pre-heated oxygen containing gaswith the stream comprising metal chlorides, wherein the walls of thetubular reactor are cooled externally to a temperature range of fromabout 0 to 500° C. and wherein the temperature of the combined oxygencontaining gas, metal chlorides and scrubbing media streams is greaterthan temperature T_(Rx), which is the minimum temperature required toinitiate oxidation of the metal chlorides, and wherein the combinationof v_(Ox), v_(mx) and v_(s) provides at least enough energy to thescrubbing media so that the media removes wall deposits as fast as thedeposits are formed.

In the present process the walls of the tubular reactor are cooled to atemperature of from 0 to 500° C., and it is more preferred to cool asubstantial portion of the walls of the tubular reactor to a temperatureof from 250 to 400° C. The walls may be cooled in two or more stages tointermediate temperatures of from 0 to 500° C. or to temperatures from250 to 400° C.

In the present process it is also preferred that the temperature T_(Rx),which is the minimum temperature required to initiate oxidation of themetal chlorides, be sustained for at least 0.1 seconds after thepre-heated oxygen-containing gas contacts the stream containing themetal chlorides.

In the present process it is also preferred that scrubbing media is fedinto the reactor at one or more positions wherein the positions areselected from the group consisting of (a) one or more positions locatedbetween the position where the pre-heated oxygen containing gas entersthe reactor and the position where the pre-heated oxygen containing gasand stream comprising metal chlorides are contacted, (b) one or morepositions located downstream of the location where the stream comprisingmetal chlorides is fed into the reactor, and (c) a position or positionswhere the scrubbing media is fed simultaneously with the streamcomprising the metal chlorides. Suitable scrubbing media may be selectedfrom the group consisting of SiO2, ZrO2, TiO2, Fe2O3, beach sand,titanium ore, olivine, garnet, titanium carbide, dolomite, petroleumcoke, salt, and like materials. In the present process, the metalchloride stream may be added by a tee mixer, an axial slot, a radialslot, and a coaxial center-feed nozzle.

The present process also includes a tubular reactor useful in therecovery of chlorine from a stream comprising metal chlorides, thereactor having a feed end and an exit end separated by a length of wallhaving a diameter D and wherein disposed in the wall near the feed endof the reactor are two or more means for feeding two or more feedstreams comprising (a) a first stream comprising hot oxygen, (b) asecond stream scrubbing media, and (c) a third stream comprising a metalchloride stream wherein the third stream is fed through a third meansfor feeding or fed simultaneously with the scrubbing media and whereinthe reactor includes a means for pre-heating at least one of the feedstreams and wherein the diameter D is varied along the length of wall ofthe reactor and wall temperature is controlled by an external coolingmeans at least over a portion of the wall's length.

It is preferred that the present reactor have walls cooled by means of ajacket having one or more pair of inlets and outlets through which oneor more cooling fluids are circulated to control the wall temperature.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 illustrates a reactor design exemplified in Example 1.

FIG. 2 illustrates a reactor design exemplified in Example 2.

FIG. 3 illustrates one method of introducing a swirl component into thefeed stream flows in the reactor.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a process and reactor designed to recoverchlorine from a stream of chlorides containing iron chlorides andmixtures of transition metal chlorides. One such chloride-containingstream is the waste stream from making titanium tetrachloride fromtitanium/iron containing ores. For example, in making titaniumtetrachloride from ilmenite ores and other iron rich ores one of theby-products is a stream rich in iron chlorides and mixed with othertransition metal chlorides. Other metal production processes that wouldproduce similar iron chloride-containing waste streams include such asthe processes to recover zirconium, aluminum, vanadium, tantalum,niobium, molybdenum, chromium, tungsten, and nickel from iron-containingores. The present process is suitable to use to recover the chlorinevalue from any stream of containing iron chlorides and other metalchlorides. The process comprises the steps of:

(a) feeding a pre-heated oxygen containing gas into one end of a tubularreactor;

(b) contacting the pre-heated oxygen containing gas at temperatureT_(Ox) and velocity v_(Ox) with a stream comprising metal chlorides attemperature T_(mx) and velocity _(Vmx) wherein the metal chlorides areselected from the group consisting of iron chlorides and mixtures oftransition, alkali and alkaline-earth metal chlorides existing in theform of entrained solids, entrained liquids, vapors and mixturesthereof;

(c) introducing non-reactive scrubbing media at temperature T_(s) andvelocity v_(s) into the reactor; and

(d) at least partially reacting the pre-heated oxygen containing gaswith the stream comprising metal chlorides, wherein the walls of thetubular reactor are cooled externally to a temperature range of fromabout 0 to 500° C. and wherein the temperature of the combined oxygencontaining gas, metal chlorides and scrubbing media streams is greaterthan temperature T_(Rx), the minimum temperature required to initiateoxidation of the metal chlorides and wherein the combination of v_(Ox),v_(mx) and v_(s) provides at least enough energy to the scrubbing mediato remove wall deposits as fast as the deposits are formed.

The present invention also includes a reactor that is suitable for usein the present process. The reactor is tubular and has a feed end and anexit end separated by a length of wall having a diameter D and whereindisposed in the wall near the feed end of the reactor are two or moremeans for feeding two or more feed streams comprising (a) a first streamcomprising hot oxygen, (b) a second stream comprising scrubbing media,and (c) a third stream comprising a metal chloride stream wherein thethird stream is fed through a third means for feeding or fedsimultaneously with the scrubbing media and wherein the reactor includesa means for pre-heating at least one of the feed streams and wherein thediameter D is varied along the length of wall of the reactor and walltemperature is controlled by an external cooling means at least over aportion of the wall's length. Examples of reactors according to thepresent invention are shown in FIGS. 1, 2, and 3.

In the present process an oxygen-containing gas is pre-heated. Thetemperature of the pre-heated oxygen-containing gas must be sufficientto attain T_(Rx) upon combination with the metal chloride and scrubsstreams, considering the temperatures, compositions and flowrates ofthose streams as well as heat losses. T_(Rx) will depend upon thecomposition of the metal chloride-containing stream and typically rangesfrom 400° C. to 800° C. Useful oxygen pre-heat temperatures wouldtypically be in the range of 1000° C. to 2500° C. The oxygen-containingstream can be heated to temperatures in this range by direct or indirectmeans including by a burner, a pebble heater, an electrical resistanceheater, or a plasma torch.

The oxygen-containing gas should contain at least, or more than, theamount of oxygen needed to stoichiometrically oxidize the metalchlorides. It may contain, in addition, inert gases such as nitrogen andargon and/or recycled product gases such as chlorine, carbon monoxide,and carbon dioxide. The velocity of the oxygen-containing gas, V_(Ox),must be sufficient to ensure that neither the metal chloride reactantsnor metal oxide products accumulate on the reactor wall in the feedzone. The minimum V_(Ox) will depend upon the geometry of the feed zoneincluding the methods of introducing the metal chloride and scrubsstreams and the presence of swirl. Introducing the oxygen-containing gaswith a tangential velocity component can conveniently generate swirl(See FIG. 3, as an example of a method to introduce swirl). The minimumV_(Ox) will also depend upon the bulk temperature and the temperature towhich the reactor wall is cooled, within the feed zone. Usefulvelocities range from 200 ft/s to sonic velocity.

Non-reactive scrubbing media, scrubs, are needed to facilitate removalof wall deposits as fast as they form. The metal chloride stream, asavailable to the process, may already contain sufficient scrubs. If not,scrubs may be added to that stream or, preferably, introduced to thereactor as a separate stream. Most preferably, the scrubs can beintroduced upstream of the metal chloride stream to allow them to mixwith and approach the velocity of the pre-heated oxygen-containing gas.A variety of materials and particle sizes may be effective as scrubs.Beach sand or product metal oxide particles in the 1 to 2 mm size rangeare known to be effective but other materials and particle sizes can beused. The scrubs can be conveniently introduced into the reactor bygravity flow or with a first conveying gas. The first conveying gas canbe an inert gas, air or, preferably, oxygen or a recycledoxygen-containing gas. The conveying velocity at the point of scrubsinjection should be selected to provide good mixing with the pre-heatedoxygen-containing gas stream.

The metal chlorides may be fed as vapors or liquids but, mostconveniently, are fed as solids entrained in a second conveying gas. Inthat case, the temperature of the metal chloride feed stream can rangefrom ambient up to the maximum temperature at which the feed can beconveyed without sticking. The upper end of the temperature range wouldbe most desirable, from an energy conservation standpoint, if thechlorides are already available at that temperature or can be brought totemperature with recovered heat. The second conveying gas can be aninert gas, air, oxygen or, preferably, a recycled oxygen-containing gas.The conveying velocity at the point of metal chloride stream injectionshould be selected to provide good mixing with the pre-heatedoxygen-containing gas stream.

When the scrubbing media are introduced with a first conveying gas andthe stream comprising metal chlorides are introduced with a secondconveying gas, the combination of the pre-heated oxygen-containing gasand the first and second conveying gases forms a bulk gas in thereactor. Preferably, the bulk gas has a velocity, V_(b), sufficient toremove wall deposits as fast as such deposits are formed.

The reactor diameter downstream of feed introduction can vary,maintaining adequate velocity to convey the solid reactants and productsand to scrub deposits from the walls as fast as they form. The minimumrequired velocity will be lower when more non-reactive scrubbing mediais present but will also depend upon the composition of the metalchloride feed stream, degree of conversion to oxides and the temperatureat which the reactor walls are maintained. Without cooling, harddeposits tend to form on the reactor walls, which are difficult to scrubaway. Using excessive velocity and wall cooling to minimize depositioncauses the temperature of the combined, reacting streams to drop rapidlyand also causes excessive pressure drop. To obtain desirable conversionof chlorides to oxides, the combined streams should remain above T_(Rx)for at least 0.1 sec. In the mixing zone, which can be considered toextend at east ten reactor diameters from the point at which the metalchloride and pre-heated oxygen-containing gas streams are combined, thereactor walls are preferably maintained below 150° C. and the velocityis preferably maintained above 200 ft/sec. To facilitate conversionwithout excessive heat input, the reactor walls, downstream of themixing zone, are preferably maintained between 150° C. and 500° C. andmost preferably between 250° C. and 400° C. The most preferredtemperature range is chosen to minimize both condensation of unreactedmetal chlorides and reactive deposition of metal oxides. Under theseconditions, the velocity of the combined, reacting stream can be allowedto drop to as low as 100 ft/sec. The walls of a final portion of thetubular reactor may be cooled below 150° C., if desired, to further coolthe reactor product.

The feed metal chlorides can be conveyed into the reactor from anintermediate storage bin or from a collection device that retrieves themfrom the process in which they are generated. Downstream of the reactor,the metal chlorides, at least partially converted to chlorine and metaloxides, can be quenched in water to separate the solid products from thechlorine and unreacted oxygen or the separation can be accomplished insuitable dry separation equipment such as cyclones and filters. Thechlorine can be recovered from the un-reacted oxygen by suitable meanssuch as liquefaction or adsorption, and the unreacted oxygen can berecycled.

FIG. 1 illustrates a reactor design exemplified in Example 1. In thisfigure preheated oxygen-containing gas is fed into one end of thetubular reactor at 1. The oxygen-containing gas flows through an annulusformed by the reactor wall 6 and a coaxial metal chloride feed lance 2.Scrub solids are introduced into this annulus at 5. Metal chloridesenter lance 2 at 3 and discharge at 4 downstream of the scrub solidsinlet 5. The reaction between the preheated oxygen-containing gas andthe metal chlorides starts at 4 and continues down the reactor. In thisfigure the walls of the reactor downstream of position 4 are externallycooled in two cooling zones 7 and 10. The upstream zone has a secondarypipe 7 surrounding the tubular reactor with cooling media flowingthrough the annulus formed by the reactor and the secondary pipe.Cooling media enters the cooling zone at 8 and exits at 9. Thedownstream zone has a secondary pipe 10 surrounding the tubular reactorwith cooling media flowing through the annulus formed by the reactor andthe secondary pipe. Cooling media enters the cooling zone at 11 andexits at 12. The reactor product discharges from the reactor at 13.

FIG. 2 illustrates a reactor design exemplified in Example 2. In thisFigure, preheated oxygen-containing gas is fed into one end of thetubular reactor at 1. Scrub solids enter the reactor and mix with thepreheated oxygen-containing gas at 3. Metal chlorides enter the reactorat 2 through a tee mixer downstream of the scrub solids inlet. Thereaction between the preheated oxygen-containing gas and the metalchlorides starts at 2 and continues down the reactor. In this figure thewalls of the reactor downstream of 2 are externally cooled in twocooling zones 4 and 7. The upstream zone has a secondary pipe 4surrounding the tubular reactor with cooling media flowing through theannulus formed by the reactor and the secondary pipe. Cooling mediaenters the cooling zone at 5 and exits at 6. The downstream zone has asecondary pipe 7 surrounding the tubular reactor with cooling mediaflowing through the annulus formed by the reactor and the secondarypipe. Cooling media enters the cooling zone at 8 and exits at 9. Thereactor product discharges from the reactor at 10.

FIG. 3 illustrates one method of introducing a swirl component into thefeed stream flows in the reactor. In this figure preheatedoxygen-containing gas enters at 1 and flows through feed pipe 2. Scrubsolids enter feed pipe 2 downstream of 1. Preheated oxygen-containinggas and scrub solids flow from feed pipe 2 into reactor pipe 4. Thecenterline of feed pipe 2 is offset from that of reactor pipe 4 tocreate a tangential entry point 3.

Oxygen-containing gas and scrub solids flow through an annulus formed bythe inner wall of the reactor pipe 4 and the outer wall of the coaxialmetal chloride feed lance 5. Metal chlorides enter the lance at 6 anddischarge at discharge location 7. The reaction between theoxygen-containing gas and the metal chlorides starts at dischargelocation 7 and continues down the reactor. In this figure the walls ofthe reactor downstream of discharge location 7 are externally cooled intwo cooling zones 8 and 12. The upstream zone has a secondary pipesurrounding the tubular reactor pipe 11 with cooling media flowingthrough the annulus formed by the reactor and the secondary pipe.Cooling media enters the cooling zone at of the secondary pipe at 9 andexits at 10. The downstream zone has a secondary pipe surrounding thetubular reactor with cooling media flowing through the annulus formed bythe reactor and the secondary pipe. Cooling media enters the coolingzone of the secondary pipe at 13 and exits at 14. The reactor productdischarges from the reactor at 15.

As shown in FIG. 3, the centerline of feed pipe 2 is offset from that ofreactor pipe 4 to create a tangential entry point 3. The tangentialentry point created by the positioning of the feed pipe 2 relative tothe reactor pipe 4 imparts a swirl to the oxygen-containing gas andscrub solids. The swirl maximizes the effectiveness of the scrub solidsin preventing downstream wall deposits by improving the contact of thescrub solids with the reactor wall. The swirl component of theoxygen-containing gas and scrub solids extends into downstream reactorpipe 11.

In a preferred embodiment of the tubular reactor for recovery ofchlorine from metal chlorides shown in FIG. 3 the feed pipe 2 istypically refractory-lined to minimize heat loss. The temperature of theoxygen-containing gas must be sufficient to attain T_(Rx) uponcombination with the metal chloride and scrubs steams, considering thetemperatures, compositions and flow rates of those streams as well asheat losses. T_(Rx) will depend upon the composition of the metalchloride-containing stream and typically ranges from 400° C. to 800° C.Useful oxygen temperatures would typically be in the range of 1000° C.to 2500° C. The oxygen-containing gas should contain at least, or morethan, the amount of oxygen needed to stoichiometrically oxidize themetal chlorides. It may contain, in addition, inert gases such asnitrogen and argon and/or recycled product gases such as chlorine,carbon monoxide, and carbon dioxide.

The reactor pipe 4 is also typically refractory-lined to minimize heatloss.

In a preferred embodiment, non-reactive scrub solids can be introducedat a location 20 shown in FIG. 3 to allow the scrub solids to mix withand approach the velocity of the oxygen-containing gas. In feed pipe 2the velocity of the oxygen-containing gas is equal to or greater thanthe minimum conveying velocity of the scrub solids.

A variety of materials and particle sizes may be effective as scrubs.Beach sand or product metal oxide particles in the 1 to 2 mm size rangeare known to be effective but other materials and particle sizes can beused. The scrubs can be conveniently introduced into the reactor with aconveying gas or gravity flow. The ratio of the weight of the scrubsolids to the weight of the metal chlorides is at least 0.05.

In a preferred embodiment shown in FIG. 3, the coaxial metal chloridefeed lance 5 is positioned on the centerline of reactor pipe 4. Thelance can be made of ceramic or water-cooled metal. If the lance iswater-cooled, it is desirable to coat it with a refractory insulator tominimize heat loss.

The velocity, V_(Ox), of the oxygen-containing gas flowing through theannulus formed by reactor pipe 4 and feed lance 5 must be sufficient toensure that neither the metal chloride reactants nor metal oxideproducts accumulate on the reactor wall in the feed zone. The minimumV_(Ox) will depend upon the geometry of the feed zone including themethods of introducing the metal chloride and scrubs streams and thepresence of swirl. The minimum V_(Ox) will also depend upon the bulktemperature and the temperature to which the reactor wall is cooled,within the feed zone. Useful velocities range from 200 ft/s to sonicvelocity.

The metal chlorides may be fed as vapors or liquids but, mostconveniently, are fed as solids entrained in a conveying gas. In thatcase, the temperature of the metal chloride feed stream can range fromambient up to the maximum temperature at which the feed can be conveyedwithout sticking. The upper end of the temperature range would be mostdesirable, from an energy conservation standpoint, if the chlorides arealready available at that temperature or can be brought to temperaturewith recovered heat. The conveying velocity at 7, the point of metalchloride stream injection, should be selected to provide good mixingwith the oxygen-containing gas stream. The ratio of the velocity of themetal chloride conveying gas to that of V_(Ox) must be less than 0.5.

Reactor pipe 11, downstream of discharge location 7, is typically acooled metal pipe resistant to hot chlorine and oxygen. The reactordiameter downstream of metal chloride feed introduction can vary,maintaining adequate velocity to convey the solid reactants and productsand to scrub deposits from the walls as fast as they form. The minimumrequired velocity will be lower when more non-reactive scrubbing mediais present but will also depend upon the composition of the metalchloride feed stream, degree of conversion to oxides and the temperatureat which the reactor walls are maintained. Without cooling, harddeposits tend to form on the reactor walls, which are difficult to scrubaway. Using excessive velocity and wall cooling to minimize depositioncauses the temperature of the combined, reacting streams to drop rapidlyand also causes excessive pressure drop. To obtain desirable conversionof chlorides to oxides, the combined streams should remain above T_(Rx)for at least 0.1 sec.

In the preferred embodiment of the reactor the mixing zone, extends atleast ten reactor diameters from 7, the point at which metal chloridecontacts the oxygen-containing gas. In the cooling zone 8 the reactorwalls are typically maintained below 150° C. and the velocity ismaintained above 200 ft/sec.

To facilitate conversion without excessive heat input, the reactor wallsof the downstream cooling zone 12 can be maintained between 250° C. and400° C. Under these conditions, the velocity of the combined, reactingstream can be allowed to drop to as low as 100 ft/sec.

Downstream of the reactor, the metal chlorides, at least partiallyconverted to chlorine and metal oxides, can be quenched in water toseparate the solid products from the chlorine and un-reacted oxygen orthe separation can be accomplished in suitable dry separation equipmentsuch as cyclones and filters. The chlorine can be recovered from theun-reacted oxygen by suitable means such as liquefaction or adsorption,and the un-reacted oxygen can be recycled.

EXAMPLES Example 1

A feed stream containing metal chlorides was injected at 4 via a lanceto flow concurrently into the center of an axially-flowing stream ofpre-heated oxygen-containing gas fed into the reactor at 1 and scrubbingmedia fed into the reactor at 5 as represented in FIG. 1.

The feed rate of the metal chlorides-containing solids feed was 300lb/hr. The conveying gas was oxygen fed at a rate of 18 SCFM. The metalchlorides were fed as a stream of solid particles suspended in theconveying gas. The metal chloride feed stream and the oxygen conveyinggas were fed at ambient temperature. The resultant velocity of the metalchloride feed stream combined with the conveying gas was 110 ft/sec.

The flow rate of the axially-flowing stream of pre-heatedoxygen-containing gas was 150 SCFM. This stream contained 70% oxygen and30% argon. It was pre-heated to 1450° C. using a plasma torch and wasflowing at a velocity of 440 ft/sec. This stream contained over 1200%excess oxygen needed for stoichiometric oxidation of the metalchlorides.

The scrubbing media of silica sand was fed at a rate of 30 lbs/hr intothe pre-heated oxygen-containing gas upstream of the metal-chloridecontaining feed addition. The mix temperature of the metal chloride feedstream, conveying gas feed stream, pre-heated oxygen containing gas, andscrubbing media stream was 960° C. The reactor inside diameter was 2″and 3″. That is, a smaller diameter in the portion following the feedzone and a larger diameter at the feed end and at the exit end. In thisExample, the reactor length (from end to end) was over 40 ft. Thereactor pressure was 23 PSIA. The residence time was 0.27 seconds.Conversion of the metal chlorides to metal oxides and chlorine was over85%. Accumulation rate of adhesive product on the walls of water-cooledreactor spools, averaged over an eight-hour run, was about 0.02lbs/ft²/hr.

Example 2

A metal chloride feed stream of particles suspended in a conveying gaswas injected at 2 through a tee mixer into a stream of pre-heatedoxygen-containing gas fed into the reactor at 1 and scrubbing media fedinto the reactor at 3 as represented in FIG. 2. The feed rate of themetal chlorides was 370 lb/hr. The conveying gas was 20 SCFM ofnitrogen. The metal chloride feed stream and the nitrogen conveying gaswere fed at ambient temperature. The resultant velocity of the metalchloride feed stream combined with the conveying gas was 70 ft/sec.

The flow rate of the pre-heated oxygen-containing gas stream was 135SCFM. It was pre-heated to 1450° C. using a plasma torch. This streamcontained 100% oxygen and was flowing at a velocity of 440 ft/sec. Thisstream contained over 1300% excess oxygen needed for stoichiometricoxidation of the metal chlorides.

The scrubbing media of silica sand was fed at a rate of 60 lb/hr to thepre-heated oxygen-containing gas upstream of the metal-chloridecontaining feed addition. The mix temperature of the metal chloride feedstream, conveying gas feed stream, pre-heated oxygen containing gas, andscrubbing media stream was 640° C. The reactor inside diameter was 2″and 3″. The reactor length was over 40 ft. The reactor pressure was 20PSIA. The residence time was 0.23 seconds. Conversion of the metalchlorides to metal oxides and chlorine was about 55%. Accumulation ofadhesive product on the walls of water-cooled reactor spools during analmost eight-hour run was minimal until scrubbing media flow was lost.

Example 3

Two experiments, A and B, compared the effect of wall temperature on therate of wall deposit accumulation. In each case accumulation rate datawere taken in one foot-long test spools located 7 feet downstream of themetal chlorides feed point. The spools were located 7 feet down streamof the metal chloride feed point since the feed streams are known to bewell mixed in this region of the reactor. In experiment A, the testspool was cooled with water while in experiment B an air-cooled testspool was used, allowing higher wall temperatures. In both cases, 80 to90% metal chloride conversions were measured at the end of the reactorwhile processing 350 pounds per hour of metal chloride-containing feedover a period of about four hours. The following data were recorded:Experiment A B Inside Wall ° C. 130 350 Temperature (estimated) BulkTemperature ° C. 880 860 Bulk Velocity Ft/s 146 140 Sand scrubs ratePounds/hour 96 70 Deposit rate Pounds/ft²/hr 0.017 <0.004

In the above Table, the inside wall temperature was estimated from heattransfer calculations using the Bulk temperature, cooling gas flow rateand inlet and outlet temperature of the cooling gas. Bulk temperature,sand scrubs feed rate and deposit rate were measured. Bulk velocity wascalculated from the measured gas feed rates, reactor geometry, and thetemperature and pressure in the reactor.

Because of the high surface to volume ratio in a small-scale reactor,cooled walls could not be used throughout. Insulated walls were used formost of the balance of the reactor in all examples. Typical depositionrates in those portions of the reactor, where wall temperatures normallyexceeded 600° C., were 0.3 to 0.5 lbs/ft²/hr.

1. A process for recovering chlorine by oxidizing a stream comprisingmetal chlorides, comprising the steps of: (a) feeding a pre-heatedoxygen containing gas into one end of a tubular reactor; (b) contactingthe pre-heated oxygen containing gas at temperature T_(Ox) and velocityv_(Ox) with the stream comprising metal chlorides at temperature T_(mx)and velocity _(Vmx) wherein the metal chlorides are selected from thegroup consisting of iron chlorides and mixtures of transition, alkaliand alkaline-earth metal chlorides existing in the form of entrainedsolids, entrained liquids, vapors and mixtures thereof; (c) introducingnon-reactive scrubbing media at temperature T_(s) and velocity v_(s)into the reactor; and (d) at least partially reacting the pre-heatedoxygen containing gas with the stream comprising metal chlorides,wherein the walls of the tubular reactor are cooled externally to atemperature range of from about 0 to 500° C. and wherein the temperatureof the combined oxygen containing gas, metal chlorides and scrubbingmedia streams is greater than temperature T_(Rx), the minimumtemperature required to initiate oxidation of the metal chlorides andwherein the combination of v_(Ox), v_(mx) and v_(s) provides at leastenough energy to the scrubbing media to remove wall deposits as fast asthe deposits are formed.
 2. The process of claim 1 wherein the walls ofthe tubular reactor are cooled to a temperature of from 150 to 500° C.3. The process of claim 1 wherein a substantial portion of the walls ofthe tubular reactor are cooled to a temperature of from 250 to 400° C.4. The process of claim 1 wherein the walls of the reactor are cooled intwo or more stages to intermediate temperatures of from 0 to 500° C. 5.The process of claim 1 wherein the temperature T_(Rx) is sustained forat least 0.1 seconds after the pre-heated oxygen-containing gas contactsthe stream containing the metal chlorides.
 6. The process of claim 1wherein the scrubbing media is fed into the reactor at one or morepositions wherein the positions are selected from the group consistingof (a) one or more positions located between the position where thepre-heated oxygen containing gas enters the reactor and the positionwhere the pre-heated oxygen containing gas and stream comprising metalchlorides are contacted, (b) one or more positions located downstream ofthe location where the stream comprising metal chlorides is fed into thereactor, and (c) a position or positions where the scrubbing media isfed simultaneously with the stream comprising the metal chlorides. 7.The process of claim 6 wherein immediately downstream of the positionwhere the stream comprising metal chlorides is fed into the reactor, apurge gas is introduced through a purged wall of the reactor.
 8. Theprocess of claim 1 wherein the scrubbing media is selected from thegroup consisting of SiO2, ZrO2, TiO2, Fe2O3, beach sand, titanium ore,olivine, garnet, titanium carbide, dolomite, petroleum coke, salt, andlike materials.
 9. The process of claim 1 wherein the pre-heated oxygencontaining gas is heated to a temperature of from 1000 to 2500° C. 10.The process of claim 1 wherein the pre-heated oxygen containing gas isheated directly or indirectly.
 11. The process of claim 1 wherein thepre-heated oxygen containing gas is heated by a burner, a pebble heater,electrical resistance heater, and plasma torch.
 12. The process of claim1 wherein the stream comprising metal chlorides is added by one or moremeans selected from the group consisting of a tee mixer, an axial slot,a radial slot, and a coaxial center-feed nozzle.
 13. The process ofclaim 1 further comprising introducing a first conveying gas with thescrubbing media and a second conveying gas with the stream comprisingmetal chlorides and wherein the combination of the pre-heated oxygencontaining gas, and the first and second conveying gases forms a bulkgas in the reactor.
 14. The process of claim 13 wherein the bulk gas hasa velocity V_(b) sufficient to remove wall deposits as fast as suchdeposits are formed.
 15. The process of claim 13 wherein the first andsecond conveying gas is selected from the group of gases consisting ofoxygen, process product gas, nitrogen, carbon monoxide, carbon dioxide,inert gases and mixtures thereof.
 16. The process of claim 1 wherein theoxygen content of the oxygen containing gas is at least the amountneeded to stoichiometrically oxidize the metal chlorides content presentin the stream comprising metal chlorides.
 17. The process of claim 1wherein the stream containing metal chlorides is injected concurrentlyinto the center of an axially-flowing stream of pre-heated oxygencontaining gas and scrubbing media.
 18. The process of claim 17 whereinthe position and relative geometry where the preheated oxygen is fedinto the reactor relative to the position where the pre-heated oxygencontaining gas and the stream comprising metal chlorides are contactedis modified to impart a swirl component into the velocity of thepreheated oxygen containing gas.
 19. The process of claim 1 wherein theratio of the weight of scrubbing media to the weight of metal chloridespresent in the stream comprising metal chlorides is at least 0.05. 20.The process of claim 17 or 18 wherein the ratio of the velocity of theoxygen containing gas to that of the metal chloride conveying gas is atleast 2 to
 1. 21. A tubular reactor useful in the recovery of chlorinefrom a stream comprising metal chlorides, the reactor having a feed endand an exit end separated by a length of wall having a diameter D andwherein disposed in the wall near the feed end of the reactor are two ormore means for feeding two or more feed streams comprising (a) a firststream comprising hot oxygen, (b) a second stream comprising scrubbingmedia, and (c) a third stream comprising a metal chloride stream whereinthe third stream is fed through a third means for feeding or fedsimultaneously with the scrubbing media and wherein the reactor includesa means for pre-heating at least one of the feed streams and wherein thediameter D is varied along the length of wall of the reactor and walltemperature is controlled by an external cooling means at least over aportion of the wall's length.
 22. The reactor of claim 21 wherein thestream comprising metal chlorides is fed by one or more means selectedfrom the group consisting of a tee mixer, an axial slot, a radial slot,and a coaxial center-feed nozzle.
 23. The reactor of claim 21 whereinthe scrubbing media particles are fed by one or more means selected fromthe group consisting of a tee mixer, an axial slot, a radial slot, and acoaxial center-feed nozzle.
 24. The reactor of claim 21 wherein aportion of the reactor's wall is a purged wall.
 25. The reactor of claim20 wherein the gas comprising hot oxygen is fed first into the reactor,followed by scrubbing media forming a combined feed stream of hot oxygengas and scrubbing media which is then contacted by the feed streamcomprising metal chlorides.
 26. The reactor of claim 21 wherein thescrubbing media is fed into the reactor at one or more positions whereinthe positions are selected from the group consisting of (a) one or morepositions located between the position where the preheated oxygencontaining gas enters the reactor and the position where the pre-heatedoxygen containing gas and stream comprising metal chlorides arecontacted, (b) one or more positions located downstream of the locationwhere the stream comprising metal chlorides is fed into the reactor, and(c) a position or positions where the scrubbing media is fedsimultaneously with the stream comprising the metal chlorides.
 27. Thereactor of claim 21 wherein the walls are cooled by means of a jackethaving one or more pair of inlets and outlets through which one or morecooling fluids are circulated to control the wall temperature.
 28. Thereactor of claim 21 wherein the means of pre-heating gas is selectedfrom the group consisting of a burner, a pebble heater, electricalresistance, heater and plasma torch.